Machine shops, structural steel plants, manufacturing facilities, and the like may employ machines for shearing metal workpieces, such as steel stock of various shapes and sizes. One type of machine, commonly known as an "ironworker" or "universal steelworker", performs various different metal working processes on workpieces at various separate stations. Typically there is a punching station for punching holes or other shapes, a notching station for notching the edge of a workpiece, and a bar stock shearing station for shearing lengths of round or square bars or flat stock.
An example of such an ironworker design is described in the U.S. Pat. No. 3,866,522. The ironworker machine employs a single, large arm or beam which is pivotally mounted to a frame and which is operated with a hydraulic piston and cylinder actuator. The various stations, such as a punching station,.a shearing station, and a notching station, are defined at various locations along the length of the pivotally mounted beam. At each station, a particular tool is mounted on the beam for movement with the beam relative to a die or other, cooperating, fixed tool on the frame. Such an ironworker design provides the advantages of simple operation and low cost.
In a typical arrangement of the conventional pivoting beam ironworker machine, the height to which the cutting or punching tool rises above the workpiece, the top of stroke position, must be set according to the thickness of the workpiece. To facilitate meeting safety standards, as well as workplace efficiency requirements, manual push buttons, selector switches, foot switches and limit switches are provided to control the operation of the various tools.
Typically, one pair of limit switches is provided for each tool. The limit switches are positioned to correspond to the top and bottom of stroke positions and are used, through relay control logic circuits, to stop and reverse tool movement, respectively. However, each time the thickness of the workpieces change, the limit switches must be reset to account for the reduced or increased stroke required. Accordingly, it would be desirable to provide an improved system and process for controlling the stroke positions of the various tools on a multi-station metal working machine without the use of limit switches. This would permit efficient setting of the top and bottom stroke positions without the necessity to reset limit switches often.
The present invention provides an improved system and process for sensing and controlling the stroke positions of various tools on a multi-station metal working machine. The improved system and process accommodate continuous sensing of stroke position and provide for readily resettable top and bottom stroke positions without the necessity to reset limit switches.